The present invention relates to a vehicle height control apparatus responsive to power steering operation and more particularly to a control apparatus well suited for controlling the height of a vehicle through suspensions provided with variable damping force-type shock absorbers.
Automobile power steering systems, particularly electrically-operated power steering system of the type in which the steering operation by a driver is assisted by use of an electric motor, is disclosed for example in Japanese patent unexamined publication Nos. JP-A-55-76760 and JP-A-61-215166. On the other hand, there are disclosed for example in Japanese Patent Publication Nos. 62-9448 and 62-9449 methods for controlling the height of the body of an automotive vehicle during its straight or corner driving.
With these conventional techniques, the power steering and the vehicle height control are independently controlled and each of these controls requires sensors such as a torque sensor and a vehicle speed sensor. Further, in the vehicle height control in which means is provided for changing the damping force of the shock absorbers to control the incline of the vehicle body, since the moving angle of the steering wheel is detected to use it as a command for varying the damping force of the shock absorbers, it involves disadvantages in that the vehicle body goes down or dives rapidly during the period of cornering and also the restoration of the vehicle body position is delayed after returning to the straight driving thus deteriorating the steering stability and that the response to the continuous steering is slow and so on.
Also, with the vehicle height control, it is conceivable to use a method in which the incline of the vehicle body is detected by using a G sensor generally used for detecting an acceleration of the vehicle to control the position of the body. This method, however, has a disadvantage that it is hardly put to practical use due to the high cost of the G sensor.
Further, U.S. Pat. No. 4,577,716 discloses a system in which the steering force by a driver is assisted by use of a servo motor.
However, none of the prior arts discloses a vehicle height control apparatus co-operating with a power steering apparatus.
Although U.S. Pat. No. 4,566,718 discloses a technique of controlling the suspensions to adjust the height of a vehicle, it does not disclose a technique of controlling the damping force of the suspensions in response to the steering torque.